Insulator



Jan. 15, 1935. M. H. HUNT ET AL INSULATOR Filed July 5, 1931 2 Sheets-Sheet l INVENTOR5. Add Fa e0 ff flu? 7 and eaya MBar-Povv.

ATTO EY 5/ NM 5 m i Jan. 15, M. H HUNT ET AL 1,987,683

INSULATOR Filed July 3, 1931 2 Sheets-Sheet 2 W/T/VE55E5 INVENTORS Margo en f/unf' and ado/ye I BY name as is, was 1,987,683

UNlTED STATES RATE-NT OFFICE INSULATOB Ionian 1!. Hunt, Parkenbnrg, W. Va.. and wearing a size: 'a 'innu rin c an ac r cuperation of Pennsylvania Application m, s, 1931, Serial No. 548,588

s can". (Oi. 9140.1)

Ominvention relates to electrical insulators glaze, and thereby occasions undue labor and exand particularly to means for reducing electropense. static discharges thereon. A solder coat also, requires an under coat or An object of our invention is to prevent radio flux to adhere with any satisfactory degree of interference and to overcome other objectionable tenacity; a sprayed-on coat of solder, copper, or I r lt all caused by electrostatic disany other material of which we are aware not becharges between the electrodes or terminals and ing highly satisfactory or permanent, s ch the dielectric bodies of insulators. coats are subject to peeling from the porcelain Another object of our invention is to facilitate surface.

the coating of dielectric bodies with conducting Where a sanded under surface is provided, a 10 and semi-conducting materials, such as metals sprayed copper or other coat adheres better but and the oxides thereof. even this structure has not taken a place amongst Another object of our invention is to provide the recognized successful articles of the art, is an insulator that shall be simple and durable expensive and is not of the simple, economical in construction, economical to manufacture and and permanent character of my invention. 15 eiiective in its operation. A coat made by rubbing carbon particles into In high voltage on line practice, a porcelain surface is more or less uncertain and electrostatic discharges occur between the metal irregular in character, is not solid like a sheet of and the dielectric parts of insulators, as'between metal, is limited in its application and has other 0 the metal cap or pin and the porcelain body of undesirable qualities. an an insulator of one type and between the tie-wire Other suggestions require special kilns n or cable and the dielectric body of an insulator heating operations, and are objectionable. of another type. These discharges cause inter- It is our aim to provide a permanent and deference with radio reception. sirable coat for a porcelain insulator that shall be 5 To overcome this objection, it has been sugreduced to sustantially the minimum of cost and 85 gested to modify the surface resistance of the inmanufacturing difficulty or, in eflect, become sulators by coating the surfaces in various ways, almost as simple in application as a coat of paint, but porcelain, the mm extensively used dielecbut which shall be' substantially as permanent tric material, resists to a high degree the provias a silicate or metallic-glaze coat and be very sion of a simple, economical and permanent strong. In this aspect, it is not only as good 80 metallic or conducting coat. for preventing radio interference as any sug- Various suggestions have been made, includgestion of which we are aware, but it more nearly ing the suggestions of coating the porcelain with approaches metallic glaze in tensile strength or metallic glaze, an electrolytically-deposited fllm, adherence to the porcelain than any other coat 5 a solder coat, a sprayed coat over a smooth or of which we are aware. as roughened surface, carbon particles rubbed into Figure 1, of the accompanying drawings, is a the porcelain and various other expedients. view, in elevation, of the top unit of a multi-part While each 0 the Prior gestions may be insulator of the pin type, showing diagrammatmade to opera su si m qumions 0! 00st ically how the unit may be spray-coated while and durability have not been solved in a satt tm isfactory ma n Figs. 2, 3, 4 and 5 are similar views of the unit The metallic Blaze require! separate mm at successive stages of production, to be hi 60mm, must be pmced Fig. 6 is an enlarged detail view in section silicat s This Mm is wamnted in of a fragment of the unit shown the other many applications, however, because a metal coat figures and 45 has 9 uses bead reducing radio interfer- Figs. 7, 8 and 9 are views, similar to Fig. 1, of ence, the metallic-glaze coat adhering to the porc e1 am with the highest degree or tawny or any modified forms of our invention. of which we are mt Referring to Fig. 1, the insulator, which is a when metallic glaze, in the raw state, is plac d preferred embodiment of the invention but illus- 50 over bare porcelain, or, in other words, over m d trative of only one of several embodiments, comporceiain which has not been coated with silicate W es 8 body Portion a Petticoat or surfaceglaze, it is obsorbed by the porous porcelain. 9 88 flange 4, a head 5 including a tie-wire An electrolytically-deposited coat requires a groove 6, a bea 0 flange 8 n a P rti n 10 conducting under coat, as of carbon or metallic through which extends a cable-receiving groove 55 or channel at right angles to the structure, as viewed in the drawings. 1

As illustrated in Fig. 1, the insulator is in a state just previous to firing and, being of porcelain, is of a substantialy light buff or cream color before being coated, as by dipping or by the use of a spray gun 12. In the condition indicated, the insulator is of a relatively hard, chalky consistency having a smooth surface. Being a solid of revolution, a prefered method of coating is to rotate the insulator, while operating the spray gun, to ensure an evenly distributed coat.

A preferred spraying material, indicated as having been partially deposited on the insulator of Fig. 1 at the top thereof, is ofa light-slate gray color and comprises water, copper oxide and a substantial quantity of inert filler material, such as calcined zinc oxide, red oxide of iron, china clay, and the'like.

The fluid composition may comprise one or more of the inert materials, in proportions of from ten to eighty per cent of the solids. The ifiert materials are provided to give body or viscosity to the resulting mixture, so that it will be deposited in a uniform layer and be self-supporting while drying, and not run by gravity to form overlaps, waves or beads.

A preferred coating liquid comprises, as its solid constituents, forty to fifty per cent copper oxide and sixty to fifty per cent zinc oxide, with enough water'to allow the liquid to wet the porcelain and firmly adhere thereto.

Fig. 2 shows the unfired insulator, with the parts 4, 6, 8 and 10 covered with the slate-gray coatingmaterial and the part 2 of its natural porcelain color. The part 2 and underside of the petticoat 4 are next coated with silicate glaze (not shown), after which the insulator is placed in a kiln and fired, in a usual manner, to vitrify the porcelain.

Fig. 3 shows the insulator, after it has been 1 fired, with the slate-gray coating turned to a dull deep black and the silicate glaze, which was, originally gray, turned to a mahogany brown or any other selected color, depending upon the constituents used.

The microscopic action occurring during the kiln firing is not exactly .known ,but, in any event, the resultant structure is a usualporcelain insulator, with an oxide coating on it which, when reduced to metal, requires several thousand pounds tension per square inch to dislodge it.

Particles of the porcelain, the copper oxide and the inert filler .becomethoroughly mixed and vitrified together in a homogeneous solid mass to a substantial depth in the insulator surface, with particles of the oxide constituting an outer stratum of substantial thickness and so homogeneously united as to provide a continuous or fluid-impervious film.

The black copper oxide covering, as indicated in Fig. 3, may be reduced to a brilliant copper coat that appears to be an integral part of the insulator.

As indicated in Fig. 4, a preferred method of reducing the copper film from the oxide coat,

, is to place the insulator in an acid bath including nascent hydrogen caused by the addition of powdered zinc; the operation being facilitated by rotating the insulator and rubbing the surface, as by a brush 14. During this operation, which is exceedingly simple, the bright copper layer appears quickly and the insulator is finished.

Fig. 5 illustrates the device as assembled in service between terminals 16 and 18, in the form of a cable or tie-wire and a pin, respectively; an attempt having been made, by shade lines, to bring out the distinction between the copper plated upper shed 4 and a lower shed 20 that is coated with a usual silicate glaze of mahogany, chocolate or other hue.

In Fig. 6, a section of the shed 4 is illustrated with the upper copper coat and the lower silicate-glaze coat merging at a line 22 which may be any place on the shed.

In Fig. 7, the line 22 extends around the shed at a position between the upper and lower limits thereof.

Ordinarily, where the shed is covered entirely with silicate glaze, electrostatic discharges occur in the intense electrostatic field between the tiewire or cable and the insulator surface to cause radio interference. This discharge is reduced or eliminated entirely by the metal coat in accordance with its texture, shape and thickness, depending upon the voltage employed; it being feasible to grade and revise the coat in various ways, as by cutting out regular areas of it, by electroplating it, by soldering to it, by oxidizing it, by exposing it to the weather and by other means.

One method of grading the resistance of the coating is to only partially reduce the metal from the oxide. This effect can be produced by applying a paste comprising powdered zinc and strong sodium hydroxide. After remaining on the insulator a certain length of time, the paste may be washed oil; the copper being reduced only where the surface was coated, or only partially reduced, depending upon the strength of the paste and the length of time it is allowed to remain on the oxide.

Fig. 8 indicates an insulator coated partially with metallic copper and partially with copper oxide. That is, it has a composite coat of both materials intermingled with each other.

In Fig. 9, a line 23 about the-shed 4, marks a division between copper, copper oxide or a mingled coating of both, disposed above the line, and copper oxide or silicate glaze below the line in which case, the resistance of the coating is graded not only in accordance with its thickness and consistency but also, in accordance with its area:

the line 23 defining fingers or projections 24 of' varying eras-sectional area projecting outwardly from an annular portion 25 of the coating on the flange 4 toward the supporting pin (not shown).

While we have shown and described particular forms of our invention, changes may be effected therein without departing. from the spirit and scope thereof, as set forth in the appended claims.

, We claim as our invention:

1. The method of coating a porcelain body which comprises applying a liquid glaze material including a metallic oxide to a portion of said body in its unfired state, firing said body to vitrify the body and glaze material, applying to a selected portion of said vitrified glaze, when cooled, a paste composed of constituents which react to produce nascent hydrogen which in turn reacts upon the glaze to reduce the metallic oxide.'

2. The method of coating a porcelain body comprising covering a portion of an unflred ceramic body with a liquid glaze material containing a metallic oxide and inert filler mixed with water, and covering an adjacent portion of the body with a liquid silicate glaze material, then firing said coated body at a temperature sufliciently high to vitrify the body and glaze materials, and reducing a selected area of the body portion covered by said metallic oxide glaze.

3. The method oi. app ying a graded resistance coating to an insulator comprising applying a 5 liquid glaze material, containing copper oxide and an inert filler, to a portion of the upper surface of the insulator before the latter is iired, and

applying a silicate glare material to the remainder of the surface, iiring said insulator to vitrii'y it and the glaze materials, and applying a reducing agent to a selected portion 01' the oxide glaze when the insulator has cooled.

MARSDEN H. HUNT. GEORGE M. BARROW. 

